The desirability of providing a handbag that can also be carried as a backpack has long been recognized. The size of handbags has steadily increased over the years as both men and women have found it highly desirable to carry bulky and sometimes heavy objects with them in connection with a variety of undertakings. Such large bags are particularly popular with students, since they permit the carrying of books, binders, calculators, etc.
While such large handbags can be carried by handles of the type which are found on a conventional satchel bag, or optionally can be carried by a shoulder strap, it has also been found to be very convenient to be able to convert such bags for carrying as a backpack.
Accordingly, various handbag strap assemblies have been provided which enable selective carrying of a bag as a handbag or as a backpack. Typical of such structures are the convertible handbags disclosed in the following U.S. Pat. Nos.: 3,938,716, 3,802,613, 3,622,056, 3,346,155, 3,019,952 and 2,515,316. These patents include carrying strap assemblies having auxiliary straps, straps that are provided with snaps that can be releasably secured at various positions on the bag, and straps that are slidably mounted to the bag.
While there is little problem in keeping an open topped bag from spilling its contents when it is carried as a satchel or handbag, once an open topped bag is converted for carrying as a backpack, the possibility of accidental discharge of its contents is great. The convertible strap structures heretofore employed in the above patents have not been suitable for maintaining the open top of the bag in a relatively secure and closed condition. Instead it has been necessary to provide auxiliary structures, such as zippers, flaps and the like, to keep the bag top from falling open when the bag is being carried in the backpack mode.
The problem of keeping the bag closed when used as a backpack can be most easily illustrated by reference to U.S. Pat. No. 3,802,613. This patent discloses a slidable strap structure in which one strap can be selectively moved to and from a position enabling the bag to be carried as a handbag and a position in which the arms of the user can be inserted between the strap and the bag to carry the same as a backpack. As will be apparent, however, since only one strap on one side of the bag is pulled to a position enabling carrying of the bag as a backpack, the top of the bag is not secure unless it is fastened, e.g., by a zipper, to the opposite side of the bag. Moreover, and equally importantly, since only one strap is slidably mounted to the bag of U.S. Pat. No. 3,802,613, the length of the strap inherently must be relatively long in order to provide sufficient slack for both of the user's shoulders when the bag is carried as a backpack. Such strap length either requires constant adjustment of the strap length or results in a strap which is undesirably long when the bag is carried as a handbag.